1. Field of the Invention
The present invention relates to a sheet feeding machine for use in a printer. The sheet feeding machine of the present invention is the detachable one that is optionally attached to a sheet feeding device of the printer. The sheet feeding machine of the present invention is useful for feeding special sheets except normal printing sheets.
2. Description of the Related Art
A conventional printer usually includes a sheet feeding machine for feeding printing sheets. For example, the sheet feeding machine has a vertically movable sheet feeding table for supporting many printing sheets thereon and sheet feeding means situated above the sheet feeding table. The sheet feeding means successively feeds the printing sheets to the printer from a topmost one as the feeding table moves upward.
In the sheet feeding machine of the conventional printer, use, thickness, quality and size of the printing sheet to be fed are limited. Generally, the only frequently-used types specified in industrial standards can be fed by the sheet feeding machine. The other types are not applicable to the machine. For example, a special card such as one comprising plural layers laminated with each other or one with its surface coated and an envelope are difficult to be stably conveyed into a printing section of the printer.
For example, the sheet feeding machine has a pick-up roller and a separating member contacted with each other to scrape the printing sheets one by one. Even if the printing sheets over two are fetched at one time, the pick-up roller and the separating member separate them from each other, so that the only one sheet is fed out. When the special cards mentioned before are fed by the sheet feeding machine, they sometimes suffer damage to a surface thereof by rubber of the separating member while passing between the pick-up roller and the separating member, or a front edge of the card may be soiled by the separating member. Further, the envelope has two different constitutions, one is that of a center portion where two sheets are superimposed on each other with air sandwiched therebetween, and the other is that of an end portion where a sheet is just bent. Thus, when the envelopes are superimposed and the pick-up roller feeds a topmost one while contacting therewith, a center portion of the envelopes are recessed while being pushed by the pick-up roller, so that a leading end portion thereof is levitated. The levitated leading end portion of the topmost envelope stops at the pick-up roller, and the envelope cannot be conveyed.
In this way, the sheet feeding machine equipped with the conventional printer cannot feed the special printing sheets stably due to occurrence of troubles such as pick-up failure, jam, damage to the sheets, levitation of the sheets, separating noise and misregistration.
The object of the present invention is to provide a sheet feeding machine capable of being detachably attached to the conventional sheet feeding machine for use in printing the special printing sheets.